General Background
The stalk of the sugarcane plant includes an outer rind which is a hard, wood-like fibrous substance. The rind surrounds a central core of pith, which bears nearly all of the sugar juice from which various sugar products are made. The outer surface of the rind has a thin, waxy epidermal layer, referred to herein as "dermax."
Certain other plants (e.g., sweet sorghum) are similar to sugarcane in that they are grasses having woody grass stalks. While there is frequent reference herein to sugarcane, it is to be understood that this invention applies to processing of woody grass stalks like sugarcane and sweet sorghum or certain of their constituents. At no point, including the claims, is any reference to sugarcane to be limiting.
Conventional sugarcane industry practices until today have utilized sugarcane primarily only for its sugar content. Such industry practices have involved chopping and crushing sugarcane stalks to remove the sugar juice, with the waste solids (bagasse) being used primarily only as fuel, mainly in sugar production operations.
Although such practices have been virtually uniform throughout the industry, it has been recognized that a number of very useful products may be produced from sugarcane if the sugarcane stalk is first separated into its rind, pith and dermax constituents. The many useful end-products made possible by such separation can provide great economic benefit. Such separation also provides significant efficiencies in the production of sugar.
Earlier efforts involving stalk separation, though not necessarily related to sugarcane, are reflected in the following United States patents:
605,293 (Madden) PA1 608,630 (Wright) PA1 616,177 (Adelsperger) PA1 623,753 (Winchell) PA1 623,754 (Winchell) PA1 627,882 (Sherwood) PA1 632,789 (Remy) PA1 657,341 (Dyer) PA1 670,037 (Sherwood) PA1 675,758 (Sherwood) PA1 684,492 (Adamson) PA1 707,531 (Adamson) PA1 1,689,387 (Heimlich) PA1 2,706,312 (Bobkowicz). PA1 3,424,611 (Miller) PA1 3,424,612 (Miller) PA1 3,464,877 (Miller et al.) PA1 3,464,881 (Miller et al.) PA1 3,566,944 (Tilby) PA1 3,567,510 (Tilby) PA1 3,567,511 (Tilby) PA1 3,690,358 (Tilby) PA1 3,698,459 (Tilby) PA1 3,721,567 (Miller et al.) PA1 3,796,809 (Miller et al.) PA1 3,873,033 (Tilby) PA1 3,976,498 (Tilby) PA1 3,976,499 (Tilby) PA1 4,025,278 (Tilby) PA1 4,151,004 (Vukelic) PA1 4,312,677 (Tilby et al.) PA1 4,572,741 (Mason) PA1 4,636,263 (Cundiff) PA1 4,702,423 (Pinto) PA1 4,743,307 (Mason) PA1 4,816,075 (Gruenewald).
Even though stalk separation efforts began as early as the late 1800's, essentially the entire sugarcane industry continued in the conventional process noted above, involving chopping and crushing of the whole stalk to extract sugar juice.
Technology in this field remained rather dormant until the 1960's, when a resurgence of development activity began, substantially all related to what has been known in the industry as the Tilby system, a cane separation system named after the principal originator, Sydney E. ("Ted") Tilby.
Broadly speaking, the Tilby system includes a multi-step operation executed by various portions of a cane separator machine. Sugarcane billets, i.e., cut lengths of cane stalk preferably about 25-35 cm long, are driven downwardly over a splitter to divide them lengthwise into semi-cylindrical half-billets. The two half-billets of a split billet are then processed individually by symmetrical downstream portions of the separator machine.
The first of such downstream portions of the separator is a depithing station which includes a cutter roll and holdback roll for milling pith away from the rind of the half-billet while simultaneously flattening the rind. The next downstream portion is a dermax removal station from which the rind emerges ready for subsequent processing in a variety of ways, including slitting, chipping and/or many other processing steps. The pith is conveyed away from the separator machine to an extraction station where its sugar juice is removed.
A significant number of patents related to the Tilby system and improvements in such system have been granted, beginning in the 1960's. These and other fairly recent United States patents related generally to sugarcane processing are as follows:
The Tilby system, when finally fully commercialized, can provide substantial outputs of several high-value products. This greatly increases cash yields per ton of sugarcane, a factor of significant importance to an industry in which profitability in recent years has been marginal at best. This is important generally, but is of particular importance to the many developing countries in which a flourishing sugarcane industry would be a boon to economic growth and stability.
Considering that sugarcane is one of the most rapidly growing, easily developed, and readily accessible sources of biomass, full commercialization of the Tilby system can significantly reduce dependence on forests and on certain other crops and resources. Among the products which can be made from sugarcane constituents separated by the Tilby system are sugar in an increased variety of forms, foods and food additives, animal feeds, a variety of wood products and building materials, alcohol for a variety of purposes, paper and other pulp-containing products, and a variety of specialty products.
While substantial technical development has occurred over a period of many years with respect to the Tilby system, a number of difficult and critical problems have remained. The failure to overcome such problems has prevented full commercialization of the Tilby system. The invention described and claimed herein is directed to the solution of certain of these problems.